1. Field of the Invention
The present invention relates to a novel silicone-modified acrylic copolymer having a polyorganosiloxane with an SiH reaction point on a side chain thereof, and to an adhesive comprising the above copolymer as a chief component.
2. Description of the Prior Art
Patients who need a denture and, particularly, a full denture, in many cases, are aged persons, and their alveolar ridges must bear an increased occlusion force per a unit area since the bone has generally been resorbed to a conspicuous degree. The mucosa of alveolar ridges becomes thin due to senile atrophy, and the occlusal stress or masticatory pressure is not softened but is directly transmitted to the alveolar bone. Moreover, a thin mucosa disposed between a hard resin denture base and the hard alveolar bone is tightened and gets hurt after every occlusion, and begins to feel pain.
In such a serious case, the resin denture base molded by using a methyl methacrylate resin (acrylic resin) that is usually used is not sufficient for stably maintaining the mastication and supporting the adhesion of the denture. That is, it is necessary to reline the mucosa surface of the resin denture base with a soft dental relining material to compensate for the lost viscoelasticity of the mucosa of the residual alveolar ridge, in order to impart cushioning property that softens the occlusal stress. That is, the object of relining with a soft material is to overcome various troubles when the thin mucosa is compressed by the hard denture base.
Examples of relatively excellent soft relining materials include room temperature-curing silicone rubbers that are cured at room temperature of not higher than 50.degree. C. and low temperature-curing silicone rubbers that cure at temperatures of from about 50.degree. to about 150.degree. C.
However, the silicone rubber-type relining materials are defective with respect to adhesiveness to the denture base. Therefore, several adhesives have heretofore been developed for adhering a silicone rubber material which is the relining material to an acrylic resin which is the denture base. For instance, there have been developed a silicone-modified acrylic resin using a copolymer of an alkyl (meth)acrylate and a dimethyl vinyl silylalkyl ester of (methy)acrylic acid (Japanese Laid-Open Patent Publication No. 43209/1990) and a silicone-modified acrylic resin using a copolymer of an alkyl (meth)acrylate and a dimethyl hydrogen silylalkyl ester of (meth)acrylic acid (Japanese Laid-Open Patent Publication No. 68007/1992).
That is, solutions in which the above resins are dissolved are applied onto the denture base and after drying, a room temperature-curing (hydrosilation reaction-curing) silicone paste which is a soft dental relining material is thickly applied thereon and is adhered being heated at about 80.degree. C. during the curing and/or after the curing.
Using the above-mentioned conventional adhesives, however, the adhesiveness is still not satisfactory between the acrylic resin which is the denture base and the silicone rubber relining material. That is, using both above-mentioned adhesives, sufficient degree of adhesion is not obtained unless they are heated at about 80.degree. C. for 20 to 30 minutes or longer.